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Heat and Mass Transfer Enhancement by Carbon Nanotubes and Supersonically-Blown Nanofibers.

機譯：碳納米管和超音速吹脹納米纖維增強了傳熱和傳質。

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The present dissertation aims at the development and study of novel nanostructured materials useful for the enhancement of heat and mass transfer at macroscopic scales. For this two novel materials were used- supersonically-blown polymer nanofibers and phase change material encapsulated carbon nanotubes.;The supersonic solution blowing was developed to form nanofibers of the order of 50 nm from several polymers. The applicability of the process was first demonstrated with Nylon 6 and then was further introduced to different other polymers to produce 50 nm nanofiber on demand.;Supersonically-blown 50 nm Nylon 6 nanofibers were introduced to filtration applications, where such nanofibers were deposited on commercial filters to filter dangerous 100 nm nanoparticles from water. Ultrafine supersonically-blown nanofibers intercepted nanoparticles more than any other nanofibers. Such nanofibers intercept nanoparticles by means of the van der Waals forces and entrap them on the windward or leeward sides. A theoretical model was also developed to study nanoparticle-nanofiber interaction and the theoretical model accurately predicts nanoparticle collection on supersonically-blown nanofibers as seen experimentally.;The applicability of supersonically-blown ultrafine PAN nanofibers in thermal management applications was investigated next. A high-power surface mimicking a microelectronic a high-power substrate was coated with supersonically-blown PAN nanofibers. In one case they were metal-plated, whereas in another one pure polymer nanofibers were used. For both cases of metal-plated and non-metal plated nanofibers, it was observed that they facilitate nucleate boiling much more than bare Cu surface and lower surface superheat by several degrees at higher heat flux. Such texturing was also robust.;Thermal management of high-power microelectronics was also tackled in the present work using phase change materials (PCM) like wax and meso-erythritol encapsulated in carbon nanotubes. Such CNTs were used to form aqueous suspensions or suspensions in oil and used in through-flow in a microchannel embedded inside a high-power "microelectronics" block. Such nano-encapsulation dramatically shortened the PCM thermal response time and prevented sticking to the wall. With an increase in the CNT-PCM wt%, cooling via PCM melting became more and more pronounced.;Finally, a comprehensive quasi-one-dimensional model was developed for multiple polymer jets issued from a die nosepiece into a high-speed air flow and deposited onto a moving screen in solution blowing process. This study is fundamental for the ongoing studies of nanofiber formation in supersonic solution blowing.
機譯：本論文旨在開發(fā)和研究新型的納米結構材料，可用于在宏觀尺度上增強傳熱和傳質。為此，使用了兩種新型材料：超音速吹塑聚合物納米纖維和相變材料封裝的碳納米管。開發(fā)了超聲波溶液吹塑法，可從幾種聚合物中形成50 nm量級的納米纖維。該方法的適用性首先在尼龍6上進行了證明，然后進一步引入到其他聚合物中，以按需生產(chǎn)50 nm納米纖維。超音速吹制的50 nm尼龍6納米纖維被引入到過濾應用中，這些納米纖維被沉積在商業(yè)上過濾器可從水中過濾出危險的100 nm納米顆粒。超細超音速吹脹的納米纖維比其他任何納米纖維都更能攔截納米顆粒。這種納米纖維通過范德華力攔截納米顆粒，并將其截留在迎風側或背風側。建立了研究納米粒子與納米纖維相互作用的理論模型，并通過實驗觀察準確地預測了在超音速吹塑納米纖維上的納米粒子的收集情況;接下來研究了超音速吹塑超細PAN納米纖維在熱管理應用中的適用性。模仿微電子高功率基板的高功率表面涂有超聲吹制的PAN納米纖維。在一種情況下，它們是鍍金屬的，而在另一種情況下，則使用純聚合物納米纖維。對于金屬鍍覆和非金屬鍍覆的納米纖維，都觀察到它們在較高的熱通量下比裸露的銅表面和較低的表面過熱促進成核沸騰的程度要高得多。這種紋理化也很魯棒。在當前的工作中，還使用相變材料（PCM）（如蠟和中碳赤蘚醇封裝在碳納米管中）解決了高功率微電子的熱管理問題。這樣的CNT被用來形成水性懸浮液或在油中的懸浮液，并且被用于嵌入在高功率“微電子”模塊內部的微通道中的流通中。這種納米封裝大大縮短了PCM的熱響應時間，并防止了其粘附在墻上。隨著CNT-PCM wt％的增加，通過PCM熔化的冷卻變得越來越明顯。最后，開發(fā)了一個全面的準一維模型，用于從模頭連接到高速氣流的多個聚合物射流然后在溶液吹制過程中沉積到移動的屏幕上。這項研究對于正在進行的超聲速吹塑中納米纖維形成的研究至關重要。

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  • 作者

    Sinha Ray, Sumit.;

  • 作者單位

    University of Illinois at Chicago.;

  • 授予單位 University of Illinois at Chicago.;
  • 學科 Mechanical engineering.
  • 學位 Ph.D.
  • 年度 2016
  • 頁碼 241 p.
  • 總頁數(shù) 241
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 遙感技術;
  • 關鍵詞

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